Bought untested ZX81 and got a black screen with a working cursor

Discussions about Sinclair ZX80 and ZX81 Hardware
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AmintaSpectrum
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Joined: Tue Jul 04, 2017 12:12 am

Bought untested ZX81 and got a black screen with a working cursor

Post by AmintaSpectrum »

Hi!

As from the title, I’ve got an untested ZX81 at an ebay auction and I get this boot up screen?

What can be the culprit?

In the next days I’ll be able to measure with an oscilloscope the ICs, ma my thanks in advance!

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Lardo Boffin
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Joined: Sat Nov 26, 2016 2:42 am

Re: Bought untested ZX81 and got a black screen with a working cursor

Post by Lardo Boffin »

All the chips are socketed by the looks of it - if you have another zeddy try chip swapping to see if that helps.
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AmintaSpectrum
Posts: 18
Joined: Tue Jul 04, 2017 12:12 am

Re: Bought untested ZX81 and got a black screen with a working cursor

Post by AmintaSpectrum »

I don't have it, but I've bought a ULA - I think is the culprit - and when I'll get it I'll update the thread!
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gammaray
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Location: Texas

Re: Bought untested ZX81 and got a black screen with a working cursor

Post by gammaray »

Is it possible that there is a composite conversion in it that needs pot adjustment? Maybe look under "RF Modulator" and see which circuit is in there.
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